Alternative food systems and networks, which have emerged around the world, are often fragmentary, reduced in size and frequently unfold in parallel, hardly linked to each other. Agroecology faces the challenge of scaling up these initiatives to gain size and a significant impact on food production and consumption. Within the agroecological movement, however, diverse conceptions exist of what a sustainable food system should be. It is thus necessary to reach an extensive consensus, from the perspective of agroecology, on the principles guiding the construction of such a system. This paper discusses the principles that would best steer the building of Agroecology-based Local Agri-food Systems (ALAS). To this end, a critical review of the scientific literature on alternative food networks and systems was performed. In so doing, we highlighted the aspects that one could consider as purely agroecological in nature and sought to bring them together to form a coherent proposal. Consequently, the present paper systematizes the main contributions of literature on alternative food networks and systems, taking into account the characteristics of sustainability from an agroecology viewpoint, and identifies the issues requiring further development. Several principles are proposed to define local food systems, based on the four dimensions of sustainability: environmental health, economic viability, social equity and the right to decide what, how and for whom food is produced.